1. Field of the Invention
The invention relates to an improved sealing assembly for a subterranean well packing unit, and particularly to a sealing assembly that minimizes extrusion of the organic sealing material commonly employed in such packing units.
2. Summary of the Prior Art
As will be later described in connection with FIG. 1, prior art sealing assemblies have involved a packing sleeve formed of an organic sealing material which snugly surrounds the tubular body portion of a packer or bridge plug for a subterranean well. The packing sleeve is subjected to substantial compressive forces by upper and lower cone elements having oppositely disposed inclined surfaces. Intermediate the inclined surfaces of both the upper and lower cone elements and the original end surfaces of the packing sleeve, a cone ring and a packer ring are mounted. Both types of these rings have to be C-rings to permit their expansion. The cone ring has an inclined surface that is cooperable with the inclined surface on the adjacent cone. An annular groove and slot effects the connection of each cone ring to a mating packer ring. Each packer ring has an inclined surface which engages with the end surface of the packing sleeve.
As the upper and lower cones are moved axially relative to each other so as to bring them closer together, an increasing compressive force is applied to the packing sleeve. At the same time, the cone rings and packer rings are expanded radially outward by the inclined surfaces of the upper and lower cones.
When the packer or bridge plug is fully set and the packing sleeve is compressed between the exterior of the tubular body and the bore of a well conduit, the substantial compression forces on the organic packing element causes a gradual extrusion of the material of such element between the inner face of the upper and lower cones and the outer surface of the tubular body. An additional major extrusion path is provided between the packer ring, the inclined surface of the cone ring, and the cooperating inclined surface of the respective upper or lower cone because of the C-ring construction of the cone ring. Such extrusion paths effect a gradual reduction in the compressive forces trapped in the organic packing element, hence reducing the sealing effectiveness of such element.
Numerous solutions have been proposed for this extrusion problem in the past, but none have been fully effective. There is a definite need therefore, for a sealing asembly which will effectively prevent extrusion of an organic packing element along the extrusion paths previously mentioned.